1. Field of the Invention
This invention relates to a display device and more particularly to a device for the electro-optical display of Indian numerals.
2. Description of the Prior Art
For the electro-optical display of characters, various categories of display systems are known, a differentiation usually being made between active (self-illuminating) and passive (non-self-illuminating) displays.
Light emitting diodes (LED) can be mentioned as an example of active display devices, and liquid crystal displays (LCD) as an example of passive display devices.
For relatively small digital display devices, such as wristwatches, pocket calculators, measuring instruments, and the like, the problem of optically legible representation of digits with the aid of digit images which can change value and place arises both in active and in passive display devices. For this purpose it is known in various types of display devices to achieve the electro-optical display of legible digits with the aid of certain grids or patterns with a multiplicity of luminous regions which can be operated, that is to say selectively activated and deactivated, individually or in groups, for example in accordance with DT-OS No. 2,461,837 with a matrix consisting of at least sixteen punctiform regions in the form of four horizontal lines each with at least three points, or in accordance with GB-PS No. 842,076 with a straight or slightly obliquely displaced rectangular pattern similar to the FIG. 8 and with a frame of six outer bars and a middle bar, which hereinafter will be referred to as a 7-segment pattern.
The last-mentioned seven-segment pattern is at present generally used for numerical display devices of the active or passive kind, that is to say based on light emitting semiconductor diodes or based on liquid crystals, because it represents an optimum compromise in respect to legibility and in respect of the electronic system required for control, even for multiplace displays.
For the mass production of numerical displays with the 7-segment pattern, for example for fully electronic wristwatches with digital display, complete modules or module components with corresponding integrated circuits and micro-processors are available.
The decade system with Arabic numerals is now generally assumed to be universally understandable. Nevertheless, precisely in Arab countries or countries with traditions steeped in Arabic, such as Iran, Pakistan, and some other Asiatic countries, the decade system is frequently used or understood not in terms of Arabic numerals but instead in terms of the so-called Indian numerals.
Numerical displays for representing Indian numerals (in some cases with certain modifications also referred to as "modern Arabic" or "original Arabic" numerals) are available on the market, but with a complex and/or difficutly legible pattern. In DT-OS No. 2,606,946 there is for example described a display device which has a store device for coded signals corresponding to multiplace numerical values and a circuit for converting the coded numerical values into two different groups of character signals, this device permitting display both in "Arabic" and in "modern Arabic" numerals. The normal Arabic numerals are displayed with the previously mentioned seven-part pattern, while for the display of the "modern Arabic" numerals corresponding to Indian numerals an eleven-part pattern and a correspondingly complex conversion are necessary.
The number of display-active parts or segments which can be operated individually in the matrix image or pattern suitable or necessary for the optically legible display of a digit is however important not only because of the different decoding and conversion, but also because of the corresponding number of connection contacts or "pins" of the components. Apart from the immediately understandable complication in the wiring of display elements with an increasing number of contact points, it is a disadvantage that the methods and components technically available for display devices for representing Arabic numerals cannot be used, or can be used only to a substantially reduced extent, for display devices for representing Indian numerals.